1. Field of the Invention
The present invention relates to a vessel propulsion apparatus.
2. Description of the Related Art
A vessel propulsion apparatus having normal rotation specifications and a vessel propulsion apparatus having reverse rotation specifications are known. A propeller having normal rotation specifications that generates a thrust in a forward direction by rotating in a normal rotation direction is attached to the vessel propulsion apparatus having normal rotation specifications. On the other hand, a propeller having reverse rotation specifications that generates a thrust in the forward direction by rotating in a reverse rotation direction opposite to the normal rotation direction is attached to the vessel propulsion apparatus having reverse rotation specifications.
A conventional vessel propulsion apparatus disclosed in U.S. Pat. No. 7,297,036 is a vessel propulsion apparatus having normal rotation specifications (which is hereinafter referred to simply as a “normal-rotation vessel propulsion apparatus”), whereas a conventional vessel propulsion apparatus disclosed in Japanese Published Unexamined Patent Application No. H11-263294 is a vessel propulsion apparatus having reverse rotation specifications (which is hereinafter referred to simply as a “reverse-rotation vessel propulsion apparatus”). Additionally, a conventional vessel propulsion apparatus disclosed in Japanese Published Unexamined Patent Application No. S63-258295 is a vessel propulsion apparatus having normal/reverse rotation specifications (which is hereinafter referred to simply as a “normal/reverse-rotation vessel propulsion apparatus”) that is capable of being used both according to normal rotation specifications and according to reverse rotation specifications.
The normal-rotation vessel propulsion apparatus of U.S. Pat. No. 7,297,036 includes a pinion (drive gear) that rotates together with a drive shaft, a first gear and a second gear that engage with the pinion, a dog clutch that is selectively connected to one of the first and second gears, and a propeller shaft that rotates together with the dog clutch. A propeller having normal rotation specifications (which is hereinafter referred to simply as a “normal-rotation propeller”) is attached to the propeller shaft. When the dog clutch is connected to the first gear serving as a forward gear, the propeller shaft and the propeller rotate in a normal rotation direction. On the other hand, when the dog clutch is connected to the second gear serving as a reverse gear, the propeller shaft and the propeller rotate in a reverse rotation direction. Therefore, the rotation direction of the propeller is switched by the dog clutch. The first gear holds the propeller shaft via a tapered roller bearing disposed between the first gear and the propeller shaft, whereas the second gear is held by a housing via a ball bearing (e.g., see FIG. 12).
The reverse-rotation vessel propulsion apparatus of Japanese Published Unexamined Patent Application No. H11-263294 includes a pinion that rotates together with a drive shaft, a first gear (reverse gear) and a second gear (forward gear) that engage the pinion, a dog clutch that is selectively connected to one of the first and second gears, and a propeller shaft that rotates together with the dog clutch. A propeller having reverse rotation specifications (which is hereinafter referred to simply as a “reverse-rotation propeller”) is attached to the propeller shaft. When the dog clutch is connected to the second gear serving as a forward gear, the propeller shaft and the propeller rotate in a reverse rotation direction. On the other hand, when the dog clutch is connected to the first gear serving as a reverse gear, the propeller shaft and the propeller rotate in a normal rotation direction. Therefore, the rotation direction of the propeller is switched by the dog clutch. The first gear is supported by a lower case via a roller bearing, whereas the second gear is supported by a housing via a tapered roller bearing (e.g., see FIG. 16).
The normal/reverse-rotation vessel propulsion apparatus of Japanese Published Unexamined Patent Application No. S63-258295 includes a pinion (gear) that rotates together with a drive shaft, a first gear (reverse gear) and a second gear (forward gear) that engage the pinion, a dog clutch that is selectively connected to one of the first and second gears, and a propeller shaft that rotates together with the dog clutch. A normal-rotation or reverse-rotation propeller is attached to the propeller shaft. When the dog clutch is connected to the first gear, the propeller shaft and the propeller rotate in a normal rotation direction. On the other hand, when the dog clutch is connected to the second gear, the propeller shaft and the propeller rotate in a reverse rotation direction. Therefore, the rotation direction of the propeller is switched by the dog clutch. Each of the first and second gears surrounds the propeller shaft, and is in a non-contact state with respect to the propeller shaft.